When ever I make lobster, I always wash it first and then put it in the freezer for about 15 to 20 minutes. It's supposed to numb the lobster.
Then I kill it like this.
***WARNING***
May not be for the faint at heart. This supposed to be the most humane way. I've made lobster this way, and also boiling it live. I can't tell the difference. Seemed to cook the same both ways.
I then proceed to boil it, adding whatever spices (normally just some salt) and then enjoying with melted warm butter.